You will need to fabricate motor mounts, after that it's similar to a car swap. A small block 727 is needed to hook up to the gen3 hemi. If you get a truck motor I believe you will have a rear sump pan. Headers and/or manifolds are going to be interesting with the narrow frame rails. Those should be the only differences, you will just then need to decide if you are going with a carb or efi.

The Gen2 hemi (I assume you mean 426) will bolt to your transmission, I am not sure about mounts and headers I assume those are straight up custom jobs. If you have headers on your 440 you will know about how much room there is to work with in that frame.